Phase Formation in the System ZrO2–LaO1.5–MnOx in Air and PO2B1 Pa After 500 h of Annealing at 12001 and 14001 deg.C

The phase relation in the ZrO2–LaO1.5–MnOx system has been experimentally determined at 1200° and 1400°C in air and at 1200°C in N2 (∼100 Pa). Tie lines between LaMnO3 and t-ZrO2 and between LaMnO3 and La2Zr2O7 are observed at 1200°C in air. The geometry of the phase diagram changes at 1400°C in air due to the appearance of a stabilized ZrO2 phase, found to be of cubic symmetry by backscattered electron diffraction. Tie lines of LaMnO3–c-ZrO2, LaMnO3–La2Zr2O7, and c-ZrO2–La2Zr2O7 are observed. At 1200°C in N2 (∼100 Pa), the LaMnO3–t-ZrO2 tie line observed at 1200°C in air is replaced by the La2Zr2O7–MnO tie line. Stabilization of c-ZrO2 is observed and a new compound forms, which is being reported for the first time. The proposed composition of the new compound is La2Zr5MnO14+δ.